Method of using intramedullary catheter

ABSTRACT

A method and device for use in delivering or withdrawing fluid to or from the vascular system of bone marrow, wherein a tubular conduit is inserted into bone and fluid is delivered or withdrawn to or from a reservoir through a seal means surrounding a head attached to one end of the conduit in communication with bone marrow at the opposite end of the conduit. Access to bone marrow is achieved by implanting an improved intramedullary catheter of the present device within a bone and creating a reusable passage via a conduit placed between bone marrow and the outer surface of bone or skin.

BACKGROUND OF THE INVENTION

This invention relates to an intramedullary catheter. More specifically,the present invention is directed toward an improved device and methodfor allowing repetitive delivery or withdrawal of fluids to or from thevascular system of bone marrow through a catheter device placed within apatient's bone.

Repetitive delivery of fluid into a patient's vascular system oftenentails an intravenous device. When a patient requires fluid during eachof numerous treatment sessions, an intravenous device must be insertedinto the patient's vein. Each time the device is inserted, the physicianruns the risk of missing the vein and injecting fluid outside the vein.Moreover, physicians often find it difficult to find a vein, or oncethey do so, numerous injections into that vein may cause its rapiddeterioration. In an effort to solve the above problems, numerousdevices are commercially available which comprise a catheter commonlyinserted into a large vein and having a self-sealing septum throughwhich repetitive injections can be made into the catheter. Thus, insteadof repetitively placing a needle into a vein, the needle can berepetitively placed through a septum and into a port attached to aconduit placed within the vein.

Intravenous catheters represent substantial improvements in the art,however, when used over a long period of time, they can cause infectionand clotting in the vein near the area where the catheter is placed intothe vein. Recently, a device and method were developed for repetitivelyplacing fluid into the vascular system via bone marrow. Such a deviceincorporated herein as U.S. Pat. No. 4,772,261 comprises anintramedullary catheter placed into a tapped bore within the patient'sbone and into the bone marrow. This device allows placement under theskin and the closing of the skin over the device such that the portionof the catheter extending outside the bone remains hidden under theskin. Although catheters placed into a patient's bone marrow representimprovements in the art, they are often difficult to place, and once inplace, are difficult to find. It is important, when placing a bonecatheter, that the head or outer-most member of the catheter be largeenough to be easily detectable (or palpable) by the physician so that heor she can target the injection needle into the septum of the catheter.Furthermore, it is important that once a catheter is in place, it besecurely held within the bone marrow and will not cause pain duringnormal patient movement. It is also important that the catheter-boneinterface be secure or tight enough so as not to leak fluid outside thebone and into the surrounding tissue. However, the base of the cathetermust be designed or shaped not to cause necrosis of the underlyingperiosteum resulting in a nidus for infection. Still further, it isimportant that a device be provided for repetitive harvesting orwithdrawing of fluid from bone marrow as well as repetitive delivery offluid to bone marrow.

SUMMARY OF THE INVENTION

Accordingly, it is desirable to produce an improved intramedullarycatheter which can be rapidly placed and securely held in a patient'sbone. The improved catheter of the present invention can either beimplanted underneath the patient's skin or can reside partially abovethe skin in a percutaneous embodiment. If implanted, the catheter isplaced within a bore made through the patient's bone and into underlyingbone marrow. A physician can feel for the catheter residing underneaththe patient's skin and thereby insert a needle through the skin and intothe catheter for delivery or withdrawal of fluid to or from thepatient's vascular system. If the device is not implanted, but is placedpercutaneous, the physician can simply visually detect the head of thecatheter and gain access to the vascular system above the patient'sskin.

The present invention includes a conduit having threads extending alongthe length of the catheter from a conically shaped head to a distal endthat, when placed, resides within the patient's bone marrow. The threadsact to securely hold the device within bone as the patient is undergoingnormal activity. The improved device is securely held in the bone with aconically shaped head extending either inside (implanted) or outside(percutaneous) the patient's skin. If implanted, the conically shapedhead allows sealing engagement with the bone adjacent the bore toprevent infection from entering the bone marrow and to prevent fluidfrom leaking outside the bone into the surrounding tissue.

In accordance with one embodiment of the present invention, a noveldevice is provided which can be implanted underneath a patient's skin.The implanted device is adapted to allow repetitive passing of fluid toa patient's vascular system via bone marrow. The implanted devicecomprises a tubular conduit with threads extending along the length ofthe conduit from a head placed at one end to the tip at the other end.By drilling a bore into the bone, the threaded conduit can be screwedinto the bore by rotational movement of a tool placed over the head.When fully implanted into the bone, the tip of the conduit resideswithin the bone marrow of the bone and the head sealingly abuts theouter surface of the bone. A seal means is provided and adapted toretain a sealing membrane on the head of the device. The seal meansincludes a silicon elastomer which permits repetitive insertion andwithdrawal of a needle without exposing bone marrow to infection. Thehead is generally conically-shaped having interior walls defining asaucer-shaped cavity covered by the seal means. The cavity is ofsufficient size to receive a needle tip and allow a fluid accessreservoir between the needle tip and the conduit (and subsequently thebone marrow). The seal means, or port to the septum, is of sufficientsize to be easily detected by the physician when placing the needle inthe implanted head. Although a physician cannot see the implanteddevice, he or she can target the needle by feeling for the underlyinghead and sealing membrane. The sealing membrane is dome shaped to aidthe physician in palpably detecting the target area.

In accordance with another embodiment of the present invention, there isprovided a device which is only partially implanted. The head portion ofthe device remains outside the patient's skin in a percutaneousembodiment. The percutaneous device is similar to the implanted devicein that it has threads on the outside of a conduit extending from aconically shaped head to the distal tip. However, unlike the implanteddevice, the percutaneous device can be inserted directly into the bonewithout having to first drill a bore into the bone. The percutaneousconduit having cutting threads placed along the outer surface of theconduit and a cutting tip at the distal tip of the threads. The threadedconduit is screwed into bone by rotating a tool placed over the head ofthe device. As the device is being screwed into the bone, cutting tipand cutting threads form a bore simultaneous with the insertion of thedevice. Thus, the percutaneous device can be placed directly into thebone without having to pre-drill a bore as in the implanted embodiment.Placement of the percutaneous device is therefore quickly performed toallow emergency delivery or withdrawal of fluid to or from the patient'sbone marrow.

In either the implanted or percutaneous embodiments, sealing engagementis made with the bone to prevent infection from entering the bone marrowand to prevent fluid from leaking from the bore. If implanted, theconically shaped portion of the head sealingly abuts the bone surfaceadjacent the bore. Thus, infection is prevented from entering the borebetween the head and the bone surface. Conversely, if the head isconfigured above the patient's skin as in the percutaneous embodiment, abutting member or protrusion sealing abuts the bone surface to preventinfection from entering the bore. Thus, as is shown here and throughoutthe following discussion, both embodiments have provisions which preventinfection from entering the bone marrow while also preventing fluidleakage from the bore. Prevention of infection and leakage is providedby a combination of the conically shaped, sealing portion of the head aswell as the sealing membrane which covers the head. Furthermore, thethreads are radially dimensioned to provide a relatively tight fit withthe bore such that little or no passage exists between the bone marrowand the outside air or overlying tissue.

In accordance with the instant invention, there is also provided a novelmethod of passing fluid to and from the vascular system of a patientthrough bone. The method includes placing an implanted device underneaththe skin in communication with the patient's bone marrow. Once placed,passage of fluid through the device and overlying skin is easilyachieved by placing a needle into the device and injecting orwithdrawing fluid therethrough. The method comprises the steps ofproviding a device having an elongated, tubular conduit with threadsextending the length of the conduit; drilling a bore into the bone;implanting the device into the bore with the conduit in operablecommunication with the bone marrow; injecting fluid through theelastomer and into the conduit for delivery through the conduit into thebone marrow and transport to the vascular system; repeating theinjecting step for repetitive delivery of fluid to the vascular system;withdrawing fluid through the elastomer from the bone marrow; and,repeating the withdrawing step for repetitive, relatively long-termdrawing of fluid from the patient's vascular system. The drilling stepcomprises making the bore of sufficient diameter to receive and securelyhold the threads of the conduit. The implanting step comprises formingmating threads to the bore in response to rotating movement of theconduit within the bore. The drilling step comprises drilling the boreextending from the surface of the bone to the bone marrow, or extendingfrom the skin covering the bone to the bone marrow. The implanting stepcomprises rotatable insertion and sealing a small portion of the outersurface of the head against the surface of the bone to prevent infectionfrom entering the bore between the outer surface of the head and thesurface of the bone.

In accordance with the instant invention, there is also provided a novelmethod of passing fluid to or from the bone marrow wherein the head ofthe device is not implanted underneath the skin. In this percutaneousembodiment, a device is provided with cutting threads extending thelength of the conduit with a cutting tip attached to the distal end ofthe conduit and a head attached to the proximal end. An elongated toolis placed over the head and the tool is rotated such that the cuttingtip and threads form a bore directly into the bone simultaneous with theplacement of the device within the bone. Upon full insertion of thedevice, a needle can be placed through the sealing membrane to passfluid to or from the bone marrow. Moreover, when the device is fullyinserted, a protrusion placed on the conduit sealingly abuts the outersurface of the bone to prevent infection from entering the bore whilealso preventing fluid from exiting the bore. It is important to notethat a bore need not be pre-drilled when using the percutaneous devicesince the percutaneous conduit is similar in function to a drill bit. Byattaching the rotating tool to the distal end and screwing the deviceinto the bone, the device functions as both a catheter and drill bit forsimultaneous placement within the bone.

If, for aesthetic reasons or for a desire to decrease the exposure ofsubcutaneous tissue to infection, the device is implanted beneath theskin, then a pilot bore must be predrilled. A drill bit is providedhaving a cutting shaft with a cutting or piercing tip placed at one endand a countersink attached near the other end. The tip is sharp toensure precise placement of the bore within the bone. Moreover, thecutting shaft increases in diameter from the tip to provide a smoothbore which is countersunk at the bone surface by the countersinkattached to the cutting shaft. The countersink produces a pilot boreentrance having a conical shape which matches the conically shaped headsuch that a fairly precise and smooth fit exists between the countersinkbore and the head. The matching of the countersink bore and the headprevents contamination or leakage therebetween. Collinear with the axisof rotation of the cutting shaft and attached to the countersink is acoupling shaft which can accommodate a rotating means such as a drill.Rotational movement provided by the drill will impart rotational cuttingmovement upon the cutting shaft and tip.

It is further appreciated that the present invention, including theconduit, head, threads, etc. can be coated or impregnated on the insideand/or outside with certain materials which can promote or inhibitcertain biological characteristics. For example, Heparin bearingmaterial may be placed on the inner surface of the conduit and saucercavity to help prevent clotting within the fluid passage. Also, e.g.,Titanium oxide can be placed on the outer surface of the buttressthreads and head to promote fixation of the present device to the boneto further secure it to the bone and help prevent fluid leakage.Antibiotics may be placed on the inner and/or outer surface to preventinfection. Still further, proteins may be placed on the distal end ofthe conduit to prevent new bone or tissue formation on said tip whichcould occlude the conduit. It is understood that any of these materialscan be either coated onto or impregnated directly into the inner orouter surface of the present device without departing from the scope andspirit of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of the percutaneous intramedullarycatheter of the present invention secured within bone and extendingpartially above the patient's skin.

FIG. 2 is a top plan view of the present invention along plane 2--2 fromFIG. 1.

FIG. 3 is a cross-sectional view of the implanted, adult-sizedintramedullary catheter of the present invention secured within bone andextending entirely beneath the patient's skin.

FIG. 4 is a sectional view of the present invention along plane 4--4from FIG. 3.

FIG. 5 is a perspective view of the disassembled intramedullary catheterof the present invention.

FIG. 6 is a perspective view of the assembled, pediatric-sizedintramedullary catheter of the present invention.

FIG. 7 is a bottom plan view along plane 7--7 from FIG. 6.

FIG. 8 is a perspective view of a twist drill bit used to produce a borewithin bone through which the implanted intramedullary catheter of thepresent invention is installed.

FIG. 9 is a perspective view of a paddle drill bit used to produce abore within bone through which the implanted intramedullary catheter ofthe present invention is installed.

FIG. 10 is a cross-sectional view of a rotating tool for engaging theintramedullary catheter of the present invention.

FIG. 11 is a cross-sectional view along plane 11--11 from FIG. 10.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, FIG. 1 illustrates a cross-sectional view ofthe improved intramedullary catheter 10 partially implanted beneath apatient's skin 12. The implanted device 10 shows head 14 extending abovethe skin and conduit 16 extending beneath the skin. The device issecurely held in place by threads 18 placed along conduit 16 and engagedwith cortical bone 20 and cancellous bone 22. Contained withincancellous bone 22 are spongy bony networks filled with venoussinusoidal spaces which forms bone marrow 24.

The embodiment shown in FIG. 1 illustrates device 10 having a catheterplaced through skin 12 in a percutaneous arrangement. A physician caninsert catheter 10 through the skin and directly into underlying bone.The distal tip 26 is designed to have one or more cutting edges forpiercing subcutaneous tissue 28 and underlying bone 20 and 22. As tip 26enters the bone similar to a drill bit entering a solid medium, threads18 further cut the bone as conduit 16 enters the passage formed by tip26 and threads 18. Once tip 26 penetrates the more dense cortical bone20, threads 18 become seated in cortical bone 20 thereby allowing foreasier penetration of tip 26 into the less dense cancellous bone 22.After device 10 is sufficiently screwed into bone 20 and 22, tip 26 willreside within the cancellous portion of bone 22 in communication withbone marrow 24. Moreover, when fully inserted, head 14, having a conicalportion 30, will abut the outer surface of skin 12. Conical portion 30will engage with the outer surface of skin 12, leaving a small gapbetween the major portion of head 14 and skin 12. Such a gap isimportant to prevent entrapment of bacteria between the head and skin.Furthermore, conical portion 30 functions to seal against the skin andprevent infection from entering subcutaneous tissue 28 via the outsideenvironment. Also, conical portion 30 maintains elevation of head 14above skin 12. The percutaneous configuration of FIG. 1 allows aphysician to quickly insert device 10 through skin 12 and intounderlying bone 20 and 22 without the necessity of pre-drilling a pilothole or bore. Device 10, having cutting threads 18, functions as a drillbit for simultaneous drilling and placement of conduit 16 intounderlying bone 20 and 22. When fully inserted, conical portion 30 ofhead 14 provides a seal thereby preventing infection from enteringsubcutaneous tissue 28 and/or marrow 24 between skin 12 and head 14. Aradially extending protrusion 35 of conical shape at the proximal end ofthe threaded conduit acts as a sealing "stop" to prevent the catheterfrom being further advanced into the bone. Moreover, protrusion 35,being of larger radial dimension than threads 18, provides a sealagainst leakage of medications or fluids from the intramedullary spaceto outside the bone. Thus, protrusion 35 prevents medications or fluidsfrom seeping from marrow 24 to subcutaneous tissue 28.

The importance of the percutaneous application of the present inventionshown in FIG. 1 is further appreciated by physicians in the field.Often, in emergency situations, it is desirable to set forth immediatefluid delivery or withdrawal procedures to or from the patient'svascular system. In doing so, many physicians, in their haste, preferthe intravenous route since access to a vein is quicker and easier thanaccess to bone marrow. However, as shown in the present invention,emergency access to bone marrow can be quickly achieved by thepercutaneous embodiment. Device 10 can be quickly screwed into bone 20and 22 in a one step procedure leaving head 14 exposed. Not only candevice 10 be quickly inserted, but repetitive, subsequent fluid deliveryor withdrawal can be achieved without having to continually enter a veinas in conventional art. Device 10 remains in place after emergencyinsertion for repetitive delivery or withdrawal of fluid to and from thepatient's vascular system without incurring the disadvantages found inintravenous delivery systems.

FIG. 2 illustrates a top plan view of head 14 shown along plane 2--2from FIG. 1. The outer portion of head 14 is shown having asubstantially circular body 32, preferably stainless steel, plastic,titanium, etc. used to encompass a sealing membrane 34. As shown inFIGS. 1 and 2, membrane 34 is dome-shaped on the exposed outer surfaceto enable a physician, nurse, or patient to easily palpate the locationof septum or membrane 34. This is important so that a needle can beaccurately inserted into membrane 34 with less chance of misguiding theneedle and injecting fluid outside of device 10. Conventionalintravenous catheters utilize a membrane or septum of the presentinvention, but do not have a palpable, easily detectable dome-shapedmembrane or septum of the present invention. Often, in intravenouscatheters, a physician may have to insert a needle many times in orderto successfully find and/or enter the device port.

By being dome-shaped and having sufficient radial dimension, membrane 34is easily located and quickly accessed by a physician. The diameter ofmembrane 34 must be large enough to provide an adequate target, but notso large as to cause discomfort or unsightliness. Preferably, thediameter of the domed portion of membrane 34 is approximately 12 mm inan adult and 10 mm in a pediatric model. It is found by the Applicantthat such a preferred size provides good target area for physicians toaccess device 10. However, diameter of membrane 34 can varysubstantially without deviating from the scope of this invention.

FIG. 3 illustrates another embodiment showing device 10 fully implantedbeneath skin 12. In circumstances where it is not essential that device10 be placed immediately, device 10 can be implanted under the skin toprovide a more aesthetic appearance and to further protect the body fromthe possibility of infection entering subcutaneous tissue 28. Dependingupon the depth of tissue 28, device 10 once secured in place will allowvarying degrees of palpability. If tissue is relatively shallow, thedome-shaped portion of membrane 34 protrudes against skin 12 or tissue28 and beyond the plane of skin 12. Thus, in shallow-tissue areas, thedome-shaped membrane 34 is visually detected by the physician to enableinsertion of a needle into the membrane. However, in areas wheresubcutaneous tissue 28 is relatively deep, palpable detection is easilyachieved due to the large radial dimensions of head 14. It is understoodthat either embodiment, implanted or percutaneous, allows the physicianto easily pass fluid to and from the bone marrow vascular system.

Illustrated in FIG. 3 is conical portion 30 which sealingly abutsagainst the outer surface of cortical bone 20. In addition to providingsealing arrangement, conical portion 30 is dimensioned to slightlyelevate head 14 above the outside surface of bone 20 such that only asmall portion of the inside surface of head 14 touches bone 20. Painduring normal movement is minimized by having only a small portion ofhead 14 pressing on the nerve-rich periosteum. Furthermore, minimizingthe contact area between head 14 and the surface of bone 20 allowsnormal circulation of the periosteum under the head thereby preventingsubstantial cell death and necrosis. Thus, when fully inserted andimplanted underneath a patient's skin 12, device 10 is configured toprevent infection from entering bone marrow from either the outsideenvironment or tissue 28 overlying bone 22. Membrane 34 and conicalportion 30 ensure such infections from happening. Further, membrane 34and conical portion 30 prevent fluid from leaking from underlying bonemarrow 24 to tissue 28.

Shown in FIG. 3 is the distal end of conduit 16 which includesself-tapping threads. Self-tapping threads may be notched in atetrahedral shape at the distal point thus permitting maximum cuttingthrough cancellous bone 22. The self-tapping feature is advantageous inthat it will save a step in the implantation procedure and will make itsimpler and faster to insert device 10 into bone 20 and 22. Instead ofhaving to tap threads into the bore, the self-tapping threads can maketheir own threads as threaded conduit 16 is screwed into the pre-drilledbore. The implanted device 10 requires only that a bore be drilled andthat threads can be made within the bore by the self-tapping feature ofthreads 18. It is important to note that although self-tapping threadsshown in FIGS. 3 and 4 utilize a tetrahedral design, any standardself-tapping design can be used, which may also include but is notlimited to a three-point notch design shown in FIG. 7.

As shown in FIGS. 1, 3, and 5, threads 18 which are self-tapping,provide quick and secure implantation of device 10 within bone 20 and22. Buttress threads can be used, and are often called ASNIS cancellousbone threads commonly found in the orthopedic industry. The threads arepreferably ten pitch, or 2.5 mm per revolution and measure 6.5 mm at thecrest and 4.0 mm at the root (basic shaft diameter). The inside diameterof conduit 16 is preferably 13 gauge or 2.4 mm. Buttress threads areuseful in withstanding uni-directional stress and have nearly ten timesthe holding power (pull-out strength and tightening torque) thanstandard machine threads placed in bone. Furthermore, 13 gauge conduitprovides a generous size that is more than adequate for the infusion offluids and medications or for the aspiration of blood and marrow. Thus,not only is it important that the inside diameter of conduit 16 besufficiently large to carry fluid, but it must also be sufficientlydimensioned to carry marrow if device 10 is used for repeated bonemarrow harvesting. Bone marrow harvesting, useful in bone marrowtransplants and/or monitoring of the bone marrow, is achieved byaspirating through membrane 34 blood, fluids or particulate matter frombone marrow 24. In applications wherein medications can suppress thebone marrow or in patients with immune deficiency disease, or whorequire frequent monitoring of bone marrow activity, the presentinvention provides a useful technique for correctly withdrawing portionsof the patient's bone marrow. In addition, the bone marrow may berepeatedly harvested for the determination of complete blood counts andall routine blood chemistries without the necessity of having to accessthe vein.

FIG. 5 is a perspective view of various components of device 10.Membrane 34 is sealed between body 32 and conical portion 30. The insidesurface of body 32 is circular to surround the outer perimeter ofmembrane 34. In addition, body 32 includes a lip 36 which engagesmembrane 34 against the outer surface of conical portion 30 whenassembled. After device 10 is assembled, the dome portion of membrane 34protrudes through the circular opening within body 32. The inner portionof head 30, which underlies membrane 34, forms a reservoir or cavitydefined by saucer 38. The reservoir or cavity is of sufficient size toaccommodate the tip of a needle inserted through membrane 34. If fluidis injected from the needle into the cavity, it is forced into the innerpassage of conduit 16. Membrane 34 permits repeated access of a needleto the reservoir such that when the needle is withdrawn, the holecreated by the needle is sealed to prevent infection from entering thereservoir. The dome-shaped portion of membrane 34 and the reservoir areof sufficient size to accommodate successful introduction of a needlefrom a wide range of angles. The floor of the reservoir is saucer-shapedto direct the needle towards the conduit 16.

FIG. 6 illustrates another embodiment of self-tapping threads having athree-point notch design rather than the tetrahedral design shown inFIGS. 3 and 4. Applicants have found that the notch design provides goodself-tapping characteristics in cortical bone. Also, FIG. 6 illustratesdevice 10 of smaller dimensions, i.e., having a radially smaller head 14and shorter conduit 16 to accommodate pediatric/small bone application.Smaller catheters are designed primarily to accommodate the smaller sizebones found in pediatric population and in small animals weighingapproximately 30-90 pounds. The length of conduit usable in smaller-boneapplications can vary drastically, however, 9 mm being a preferred size.A 9 mm tip will usually allow the distal end of conduit 16 to entermarrow 24 without impinging on the opposite wall or perforating throughthe opposite side of cortical bone 20. It is understood, however, thatconduit 16 can be of any dimension (length or width) depending upon theparticular bone size and/or fluid delivery rate. If a bone is relativelylarge, then longer catheters are preferred. Conversely, if a bone isrelatively small, then a smaller catheter with a shorter conduit ispreferred. In either case, the optimal length of catheter is chosen suchthat the distal end resides within marrow 24 and somewhere between theopposing walls of cortical bone 20.

It is further appreciated that the present device 10, including theconduit 16, head 14, tip 26, threads 18, conical portion 30, body 32,lip 36 and saucer 38 can be coated or impregnated on the inside and/oroutside with certain materials which can promote or inhibit certainbiological characteristics. For example, Heparin bearing material may beplaced on the inner surface of the conduit 16 and saucer cavity 38 tohelp prevent clotting within the fluid passage. Also, e.g., Titaniumoxide can be placed on the outer surface of conduit 16, buttress threads18, head 14 and tip 26 to promote fixation of the present device to thebone to further secure it to the bone and help prevent fluid leakage.Antibiotics may be placed on the inner and/or outer surface of conduit16, head 14, threads 18, etc to help prevent infection. Still further,proteins may be placed on the distal end of conduit 16 or tip 26 toprevent new bone or tissue formation on said tip which could occlude theconduit. It is understood that any of these materials can be eithercoated onto or impregnated into the inner or outer surface of selectiveportions of the present device 10 without departing from the scope andspirit of the present invention.

FIG. 7 illustrates a bottom plan view along plane 7--7 from FIG. 6.Self-tapping threads 30 are shown with the three-point notch designtypically used for implantation with cortical bone. Also shown isconical portion 30 extending radially outward from conduit 16 toward theunderneath side of head 14. The outer portion of conical section 30 isunderstood to engage against skin 12 (in the percutaneous embodiment) orbone 14 (in the implanted embodiment) to provide a sealing arrangementnecessary to prevent infection or fluid leakage.

FIG. 8 illustrates a dedicated drill bit 40 specifically used for theimplanted embodiment. Bit 40 serves to bore the proper size hole foroptimum fitting of the device's self-tapping threads 18 into bone 20 and22. Twist drill bit 40 comprises an elongated cutting shaft 42 havingspiral cutting edges which cut and remove cortical and cancellous bone20 and 22, respectively, in response to rotational movement placed uponshaft 44. As the cutting shaft 42 forms a bore within bone 20 and 22, acollar 47 functions to stop the drilling at the proper depth so as notto drill completely through the bone and out the other side. Thus,collar 47 prevents the distal tip of cutting shaft 42 from penetratingthe opposite wall or through the opposite wall. Countersink 46,functions to create the proper angle of the bone onto which the conicalportion of the head can seat and form a tight seal. Without thiscountersinking step, the process of making threads, either with a tap orwith the self-tapping threads, may damage the entrance into the bone towhere it may leak fluid from the bone marrow and into the surroundingtissue. The countersink dresses the bone in a smooth circular fashion topromote a sealing fit. In addition, if the countersinking step takesplace separate from the drilling, the angle of the countersink may bedifferent from the angle of the bore, again causing an irregularity withrespect to device 10, which provides a space for leaking. Shaft 44,shown at the top of twist drill bit 40, is of standard size toaccommodate a drill such that rotational movement of a drill will impartrotational movement to shaft 44 and consequently to cutting shaft 42.Shown in FIG. 9 is paddle drill bit 48 having a planar cutting shaft 50extending between the distal tip of bit 48 and countersink 46. Attachedto the opposite side of countersink 46 and collinear with the axis ofrotation of shaft 50 is shaft 44 onto which a standard drill can beattached. Similar to twist drill bit 40, paddle drill bit 48 is used toproduce a bore from the outer surface of cortical bone 20 through bothcortical bone 20 and cancellous bone 22. Either twist bit 40 or paddlebit 48 can be used to form the bore.

FIG. 10 illustrates a device driver or tool 52 useful for insertingdevice 10 either within a bore as in the implanted embodiment, ordirectly through the bone as in the one-step percutaneous embodiment.Tool 52 includes a handle 54, a neck 56 and a head 57. Placed withinhead 57 are keys or sockets 58 which engage with the flat, planarsections 60 made within the circumference of head 14. FIGS. 2, 5 and 7illustrate flat, planar sections 60 placed in head 14. The purpose ofplanar sections 60 is to provide a flat surface adapted for receivingkeys 58 such that rotational movement upon handle 54 can be transferredto device 10. The advantages in having flat, planar sections 60 is thatthere are no grooves or crevices on head 14 which can trap bacteria anddoes not cause interference with overlying tissue when implanted beneaththe skin. By engaging keys 58 with planar sections 60 and then rotatingthe handle 54, device 10 is screwed into bone 20 and 22. Handle 54 maybe in the shape of a standard screw driver handle or standard orthopedicinstrument handle with keys 58 accommodating head 14 much like a socketwrench engages a nut. Tool design has the benefit of securely holdingdevice 10 so that alignment is easily made with the pilot hole or bore.Furthermore, the smooth outer circumference of head 14 protects thesurrounding tissue during insertion. Tool 52 is relatively simple andeasy to use. Twisting motion upon handle 54 will provide necessaryrotation and insertion of device 10 within the bore. Upon fullinsertion, rotation will cease and tool 52 is quickly and easilywithdrawn. FIG. 11 illustrates grooves 58 placed within tool 52.

The foregoing description of the invention has been directed to twopreferred embodiments of the present invention. One embodiment beingpercutaneous and the other being implanted. It will be apparent,however, to those skilled in the art that modifications in bothapparatus and method of either embodiment may be made without departingfrom the spirit and scope of the invention. For example, it isunderstood that the present invention can be implanted either partiallyabove or totally below a patient's skin--in accordance with eitherembodiment. Also, the present invention can be used for repetitivedelivery or withdrawal of fluid and small particles to or from bonemarrow. Further, it is understood that buttress threads may be used forsecuring the invention within bone or a bore contained in bone. Althoughbuttress threads are preferred, other securing means or types of threadmay be used without departing from the invention. Further, the presentinvention uses various forms of self-tapping threads which alleviate theneed for tapping the bore prior to insertion of device 10. Any form ofself-tapping arrangement, including, but not limited to, the tetrahedralor three-point design can be used without departing from the invention.Still further, it is understood that conduit 16 and head 14 may be sizedto accommodate any particular bone size or shape. Therefore, it isApplicants' intention in the following claims to cover all suchequivalent modifications and variations which fall within the truespirit and scope of the invention.

What is claimed is:
 1. A method of passing fluid to and from thevascular system of a patient through bone, comprising the stepsof:providing a device having an elongated, tubular conduit with threadsextending the length of said conduit, and a head with an overlyingsilicone elastomer attached to one end of said conduit; drilling a boreinto the bone; implanting said device into said bore with the conduit inoperable communication with the marrow of said bone; injecting fluidthrough said elastomer and into the conduit for delivery through theconduit into the bone marrow and transport to the vascular system;repeating the injecting step for repetitive, relatively long termdelivery of fluid to the patient's vascular system; withdrawing fluidthrough said elastomer and from the conduit for drawing fluid from thebone marrow; and repeating the withdrawing step for repetitive,relatively long term drawing of fluid from the patient's vascularsystem.
 2. The method as recited in claim 1, wherein said drilling stepcomprises making the bore of sufficient diameter to receive and securelyhold the threads of said conduit.
 3. The method as recited in claim 1,wherein said implanting step comprises forming mating threads in saidbore in response to rotating movement of said conduit within said bore.4. The method as recited in claim 1, wherein said drilling stepcomprises drilling said bore extending from the surface of said bone tosaid bone marrow.
 5. The method as recited in claim 1, wherein saidimplanting step comprises sealing a small portion of the outer surfaceof said head against the surface of said bone to prevent infection fromentering the bore between the head and the surface of said bone.
 6. Amethod of passing fluid to or from the bone marrow of a patient,comprising the steps of:providing a device having an elongated, tubularconduit with cutting threads extending the length of said conduit, and ahead with an overlying sealing membrane attached to one end of saidconduit and a cutting tip attached to the opposite end of said conduit;placing an elongated tool over said head; screwing a portion of saiddevice into said bone in response to rotating movement of said tool; andplacing a needle through said sealing membrane to pass fluid to or fromsaid bone marrow.
 7. The method as recited in claim 6, wherein saidelongated tool is adapted to engage against at least one flat surface onthe perimeter of said head.
 8. The method as recited in claim 6, whereinsaid screwing step comprises rotating said device sufficient to placesaid tip within said bone marrow and said head outside the skin abuttingwith the skin covering said bone.
 9. The method as recited in claim 6,wherein said screwing step comprises rotating said device sufficient toplace said tip within said bone marrow and said head implanted under theskin and outside the bone abutting with the outer surface of the bone toprovide a seal.